You will find this node much more compelling (or, for that matter, disconcerting) if, before reading it, you decide upon your perceived size (moderate, average, or well endowed) and subsequently measure your penis size.

In 1942, prompted by the "clinical need" "for more thorough knowledge of normal variation in the size of male genitalia," William A. Schonfeld and Gilbert W. Beebe, performed the first widely-known penis size survey. In 54 men between the ages of 20 and 25, they measured the mean erect penis length as 5.13". This estimate appears inaccurate, given the small data set.

The classic penis size study is "Sexual Behaviour in the Human Male" due to Alfred C. Kinsey, et al (1948), which had a sample size of 3,500 subjects. In this study, each participant was given a stamped postcard against which he would hold his erect penis, mark its length, and drop the postcard in the mail. As such, the participants never even handled a ruler. In this study, Kinsey found the average erect size to be 6.2".

William H. Masters and Virginia E. Johnson's 1966 study was the first to address the "phallic fallacy", the mistaken belief that size increase during erection is proportional to flaccid length. In fact, they found that the variation in flaccid size is much larger than variation in erect size and small flaccid penises increase more in size that long flaccid penises. Their abnormally low average erect size estimate, 5.2", is perhaps explained by the small data set (312 participants).

In 1988, Paul L. Jamison and Paul H. Gebhard averaged the data from the Kinsey and Masters studies. They commented that "the variability in penis size will be likely to continue to intrigue ... specialists in the study of human sexuality, as well as the general public." They found the average erect size to be 6.21", with a standard deviation of .77", which is to say that 95% of men will not be more or less than 1.54" inches from the average value.

What is the average size of the erect penis?

This is the most frequently asked penis size question.

In addition to the above results, several informal (and perhaps inaccurate or skewed) web polls quote the following results:

In addition to average erect penis size, The Definitive Penis Size Survey contains many unexpected results regarding penis size. Some of these are presented here, in abridged form. All the results are available at http://www.sizesurvey.com/result.html

In light of potential objections that the data may be inaccurate, Richard Edwards explains his confidence in his data accuracy:
"My results are very close to that reported by Kinsey et al and the almost symmetric distribution of erect penis lengths, leads me to suspect that any residual and unavoidable contamination has been kept to a minimum."

It is interesting to note that among East Asians residing in the East, 31% felt that they were generally of modest size, compared to 56% of those living in the West. Also of interest is that african american subjects felt they were generally well endowed, "an opinion which was not borne out by the results of this study".

Average erect penis length increases until the age of 16.

"The average increase in penis size was 197.9%. However, for men whose flaccid penis measured 80 mm (3.1") or less, the increase was 263.2%, compared to 165.3% for those greater than this length."

Outside of the United States and Canada, 64% were uncircumcised. This compares to 40% of Canadians and only 15% of Americans.

Most pornstars' penises are only slightly larger than average and are definitely not in the top 5% by size.

The following excerpt from http://www.rame.net/faq/part5.html, the rec.arts.movies.eroticaFAQ addresses this point in greater depth:

Hart Williams observes:

Generally, most male penii in porn run about the same general size. For years, I heard "They're ENORMOUS!," but with a few exceptions (Holmes, Jeremy, Long Dong Silver [fave of Justice Clarence Thomas], almost all are 'a little bigger than average' (whatever the hell that means -- an actress told me). On the set, they were not intimidating, else this author is the same size and missed his calling -- and he doubts it, sincerely. Tom Byron, for instance, looks enormous, but he's pretty much the same size as anyone else. But, in his early days, he was a sub-6-foot male, and skinny, and it looked HUGE (this was a question from several early female fans of the biz).

...

Most males haven't seen another man erect close up, and the picture gives you no frame of reference as to the size of the actors, height-wise or pecker-wise. Back in the movie days, a monster shot of a spurting one-eyed- wonder-worm could be ten or twenty feet high on the screen. Talk about no frame of reference....

If you're worried about comparisons, a good way to judge is to look at the guys hands when they grab their own dicks, and compare it to yours. Most guys hands are about the same size, so you could use that as a frame of reference.

Tim Evanson, my reporter on the gay scene says:

The average gay porn star's height is 5'8". Thus any penis that looks 8" on film is probably only 6.5" or 7" in real life. Famous gay porn stars with "enormous" cocks are, really, much smaller:

Often, gay porn stars clip their pubic hair or shave it entirely, enhancing the appearance of size. Most also shave their testicles, which enhances size as well. Several use a "cock pump" to enhance vascularity and size temporarily before oral sex or anal penetration. Many stars also use cock rings of leather or steel to enhance erections and trap blood in the penis -- causing a larger look.

Also, do not compare the "realistic" dildos often marketed as "modeled from Jeff Stryker's own penis" (the most famous examples being the Jeff Stryker, Kris Lord, and Foot Long Sean Davis models) to real penis size. Firms purposefully enlarge these dildos (so says my friend, who worked as a graphic artist at one).

RJ: They say 10 in some press, and I say fine. I'll keep the extra quarter-inch. They used to say that John Holmes was 14. He wasn't. He was 12. Which is still pretty massive! That ain't nothing to be shy about. In fact, he used to call me "Little Dick." I'd say, well, listen to this. I'd say, "Well, John, with you it's not sex, it's a pap smear. Once you hit bottom, where the fuck are you going to go?" We used to make jokes about that, you know. He'd call me "Little Dick," I'd call him "Pap Smear."